The invention relates to a method for recovering the sensible heat of slag, in particular of blast furnace slag, wherein the liquid slag is allowed to solidify on the surface of a hollow cooling body provided with a liquid internal cooling and preferably designed as a cooling drum, and is indirectly cooled by the liquid internal cooling, the liquid cooling medium of the liquid internal cooling being guided in a thermodynamic cyclic process, as well as to an arrangement for carrying out the method.
A method of the initially defined kind is known from German Offenlegungsschrift No. 31 22 059 in which the slag is poured between two drums provided with internal cooling, the drum surfaces moving upwardly with the slag in the region of contact so that the slag is in contact with the drums over a long period of time and is cooled to a low temperature. The slag, which adheres to the drums over more than 3/4 of the drum surfaces, is removeable from the drums only with difficulty and by the formation of relatively large pieces of slag. The drums are heated to a relatively high temperature by the slag covering them. As cooling is started, the temperature gradient is very low, rising only after a certain period of time, whereby the desired glassy solidification of the slag is not guaranteed.
A further method for recovering the sensible heat of slag is known from German Offenlegungsschrift No. 27 59 205. With this method, the slag is poured onto what is called a centrifugal wheel, which centrifugal wheel mechanically atomizes the slag and throws it away. During the slag's travel through the air after having been thrown away, the slag cools down, with a thin, still soft skin forming on the slag particles. During the relatively short flight of the slag particles through the air, a solidification all through of the same is not guaranteed so that the slag particles tend to agglomerate when subsequently impinging on one another. Therefore, it is necessary to add a powdery separating agent, which separating agent, as it partially remains adhered to the slag particles, restricts the fields of application of the slag particles and cannot be guided in circulation entirely on account of its adhering to the slag particles; it must be renewed all the time.
According to German Offenlegungsschrift No. 27 59 205 the slag particles, together with the separating agent, reach a vessel, through which air is streaming from bottom to top, cooling the slag particles. The air heated by the slag particles, after having passed a cyclone separator, serves to heat a medium in a heat exchanger. In the fluidized bed formed within the vessel by the slag particles as a result of the passage of air, a heat exchanging tube is arranged, which is subjected to a great mechanical wear.
Apart from the fact that with this known method the glassy solidification of the slag is not ensured and a separating agent must be used, as described above, the heat recovery is also insufficient because of the cooling is predominantly effected by air.
The invention has as its object to eliminate these disadvantages and difficulties and has as its object to provide a method, as well as an arrangement for carrying out the method, which makes feasible as completely as possible a recovery of the sensible heat of the slag, wherein, however, a high percentage of glassy portions of the slag and a good grindability of the slag are ensured.